Minerals are currently being used to modify and reinforce various polymers. For instance, minerals such as silica (amorphous or crystalline), aluminum silicate, calcium metasilicate, talc, and the like, are added to thermoplastic polymers to enhance stiffness, heat resistance, strength, and to reduce shrinkage and to reduce the cost of the more expensive polymers. However, a major disadvantage of such mineral/polymer composites is that fabricated parts generally exhibit brittleness and there is, correspondingly, an alarming tendency for such parts to shatter when subjected to a sudden impact loading, regardless of the inherent toughness of the unreinforced polymer. The shattered part is rendered useless and, in general, is not repairable. On the other hand, if the plastic material had built-in shatter resistance, in many cases the impact loading would serve only to crack the part or merely result in the puncture of a small hole. In such cases, the damaged part could be repaired by standard patching procedures.
It has now been discovered that the use of glass fibers in thermoplastic compositions of high molecular weight polyesters which are reinforced with talc or mica significantly improves the shatter resistance of molded parts comprising such compositions. In addition, improvements in other properties, e.g., tensile strength, elongation, modulus, impact strength and heat distortion temperature, are also obtained.